Secrecy communication system



July 30, 1946. J. H. HAMMOND, JR l 2,404,839

SECRECY COMMUNICATION SYSTEM Filed Aug. 22, 1941 3 Sheets-Sheet 1 R. J D w RM mM, .N mA I.V VH f m5 .Y A HY NB H 0 J am I\MWX L July 30, 1946. .1. H. HAMMOND, .1R

SECRECY COMMUNICATION SYSTEM Filed Aug. 22, 1941 5 Sheets-Sheet 2 canoscan-n nnnnnnnnnnnnan PULL-Down I PULL-Down -PULL-Down |/////l FRAME 5 V//M PULL-DUWN FRAME`2.

|///| FRAMEl LIGHT FLAsHas VSCAIU lNvENoR JOHN HAYs HAMMoNn, JR.

July 30, 1946. J, H HAMMOND, JR 2,404,839

SECRECY COMMUNICATION SYSTEM Filed Aug. 22, 1941 3 Sheets-Sheet 3 Patented July 30, 1946 FFICE sEcREcY COMMUNICATION SYSTEM John Hays Hammond, Jr., Gloucester, Mass.,

assignor to Radio Corporation o1' America Application August 22, 1941, serial No. 467,891

4 claims. (ci. 17a- 6.7)

This invention relates to secrecy communication systems and more particularly to a system for communicating messages by television.

'I'he invention further relates to means for in serting a message in a single frame of a television moving picture transmission system and means for recording this message on a moving picture film. y

The inventionalso relates to means for sending a message as a single frame of a, television transmission system at a predetermined time and means for receiving the message on a photographic film.

'I'he invention also relates to a novel and improved television receiving system.

The invention also consists in certain new and original features of construction and combinations of parts hereinafter set forth and claimed.

Although the novel features which are believedv to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation and the manner of its organization may be better understood by referring to the followingr description taken in connection with the accompanying drawings forming a part thereof, in which Figure 1 is a schematic diagram of a, typical transmitter which may be utilizedin a system embodying the present invention.

Figure 2 illustrates a section of lm used in the transmitter shown in Figure 1.

Figure 3 illustrates diagrammatically the sequence of events in the transmitter shown in Figure 1.

Figure 4 is a schematic diagram of a. receiver embodying the present invention.

Like reference characters denote like parts in the several gures of the drawings.

In the following description and in the claims parts will be identified by 'specific names for convenience, but they are intended to be as generic in their application toy similar parts as the art will permit.

Referring to the accompanying drawings and more particularly to Figure 1, a standard television, film transmitter is shown comprising a motion picture projector II which projects a standard film upon an iconoscope camera I2, the output circuit of which is connected to the necessary amplifiers I3 and radio transmitter I4.

The projector I I is provided with the usual feed and take up reels I5 and I6 upon which is wound the film I1. The film I1 passes thru two gates I8 and I9 and over a number of sprockets 20, 2l

and 22 'Ihe sprocket 2I is driven intermittently by anintermittentcam and spider-follower 23 of the early Powerstype, in which the throws are cated 144 and 216 apart respectively. This mechanism is driven by a 3600 R. P. M. synchronous motor 24 thru a bevel gear and pinion 25-26 having a 5:1 ratio. Mounted on the shaft of the motor 23 is 'a shutter disc 21 which is provided with a slot 28. I

Light from a source of illumination, such as an electric arc 29 passes thru a lens system 30,

the light gate I9, film I1, and a second lens system 3| and is focused upon the iconoscope mosaic 32. The iconoscope I2 isof standard and well known construction and is provided with the usual horizontal and vertical deflection coils 35 and 36 which are connected to the deflection amplifiers 31.y `The iconoscope mosaic 32 is connected thru an output circuit 38 to the amplifier I3.

A synchronizing generator 39 is connected to the amplifier I 3 and controls the speed of the motor` 24. Control equipment 40 is -connected to the amplifier I3 and the transmitter I4 is provided with the usual antenna 4I. A light souce 42 is 25 located near the gate I8 and is focused bya lens A 43 upon a photo-electric cell 454 which is connected to the control potential means 46 which in turn is connected to the lamplifier I3. The sound head 41 is connected to the amplifier I3.

The lm I1 used in this invention may be the standard motion-picture lm with one or more of the picture frames replaced by the message 50. (Figure 2.) This replacement may be done in any lmanner well'known in the art, such as cutting the film and inserting a section bearing the message.

` Operation In the operation of the transmitter shown in Figure 1 the film I1 is movedintermittently by means of .the cam and-spiderfollower 23. The cam is driven at 12 revolutions per second by the synchronous motor 24 which runs at 3600 R. P; M. 'I'his causes the lm I1 to be pulled down at un'- -is indicated at 52 in Figure 3. These light flashes 55 are fofonly M205 second duration.

equal vintervals as the throws of the cam are lo-v ter 21 is focused upon the iconoscope mosaic 32.

This mosaic is scanned 60 times per second as indicated at 53 in Figure 3. The scanning periods 53 occur between the light flashes 52 so that the television picture signal is produced and transmitted during periods when no optical image is on the mosaic 32. During these periods, however, an electrical image is present on the mosaic 32 in the form of bound electrostatic charges on the minute photo-sensitized silver globules comprising the mosaic'32.

During the scanning periods the sensitized mosaic 32 is scanned by a moving beam of electrons 55 which is caused to scan the image on the mosaic 32 by means of the deflection coils 35 and 36 in a well known manner. The deilection coils 35 and 36 are energized from the deection amplifiers 31 which are controlled by the synchronizing generator 39 acting thru the amplifier |3. As the synchronizing generator 39 also controls the synchronous motor 24, the operator can ,make the short 1A200 second light flashes fall within the 1/300 second intervals between the vertical' scanning periods with some tolerance on each side as depicted in Figure 3.

'I'his arrangement of moving film and scanning is necessary as the standard lm moves at the average rate of 24 frames per second while the television apparatus operates at 30 frames per second and 60 fields per second, interlaced, so that the projector must flash a still picture onthe mosaic every lo of a second with each flash lasting about 9h00 second.

A fuller description of the construction and operation of the transmitter is set forth on pages 48-61 in the R. C. A. review, volume IV, 1939- 1940. It is to be understood that this particular transmitter is described merely as an example of a suitable system to which this invention may be applied and that other devices capable of scanning a motion picture lm and transmitting the scanned image may be used.

The receiver embodying the present invention is shown in Figure 4 as comprising an antenna 60 which is connected to the input of the amplier 6|, the output of which passes thru a videoamplifler 62 to a cathode-ray tube 63. An oscillator 65 is connected .to the amplifier 6| and a high voltage supply source 66 is connected to the tube 63,V The deection coils 61 and 68 of the tube 63 are connected to the deflection ampliers 69 which in turn are connnected to the sawtooth generators r10. The sawtooth generators 18 are controlled by the synchronous amplier 1| which is connected to the main amplifier 6|.

For making a photographic record of the pictures produced by the cathode ray xtube 63, a moving picture camera apparatus 15 is provided. The sensitized iilm 16 of this apparatus is unwound from a supply reel 11, passes over a sprocket 18, thru a. lm holder 19, over sprockets 80 and 8|, thru a sound recorder 82 and is wound upon a take up reel 83'.

The sprocket 80 is driven intermittently by an intermittent cam and spider follower 85, which is similar to the cam and spider-follower of Figure 1. The cam 85 is' driven by a 1:1 ratio bevel gears 86-B1, the latter being secured to a shaft 88 to which is attached a shutter disc 89. The shutter 89 is provided with two slots 90 and 9| and passes between two lens 92 and 93 which focus the television image upon the iilm 16. The shaft 88 is driven from a 3600 R. P. M. synchronous motor 95 thru a diierential 96 and a set of bevel gears 91--98 which have a 1:5 ratio. The dinerential 96 is operated by a lmurled knob 99. The motor 95 is driven from a power amplier |00 which is controlled by a frequency multiplier |6| connected to the sawtooth generators 10. The sound recorder 82 is operated by a sound amplifier |02 connected to the main amplifier 6|.

Operation In the operation of the receiver depicted in Figure 4; the television program is received by the antenna 86 and is fed to the main ampliiier 6| which, for example, may consist of a first detector, three stages of intermediate frequency amplification and a second detector and synchronizer. 'I'he output from the second detector is fed to the video amplier 62 where the picture signal is amplied and fed directly to the cathode ray tube 63. The second anode of the tube 63 is supplied with high voltage, for example, 200 volts direct current, from the full wave rectifier 66. Low voltage power may be supplied to the tube 63 from a source not shown.

The canning and synchronous control auxiliaries make use of the second stage of the second detector, which may be used as a clipper rectifier to provide the synchronous pulses separated from the picture impulses. The output of the clipper rectier leads to the synchronous amplifier 'Il which acts to separate the vertical synchronous pulses from the horizontal. The sawtooth generators 10 may include a blocking oscillator and discharge tube which may be used to develop sawtooth waves of voltage under control of the vertical impulses and a second blocking oscillator and discharge tube may be used to develop sawtooth waves of voltage for the horizontal direction. The outputs of these two circuits control the vertical and horizontal deflection ampliers 69 which in turn control the operation of the vertical and horizontal deflection coils 61 and 'I'he television picture is produced on the fluorescent screen of the cathode ray tube 63 in the usual manner, the picture signal being supplied by the video amplifier 62 and the cathode ray beam being deflected by means of the coils 61 and 68. As already described the picture on the screen will consist of two images of frame three images of yframe 2, two images of frame 3, etc. As only one image of each frame is to be photographed the disc 89 is provided with the two slots 90 and 9|, which are 144 and 216 apart respectively. The disc 89 is rotated at ts the speed of the disc 21 (Figure 1) or one revolution in 2/24 second. I'his speed of rotation is accomplished by driving the shaft 88 from a synchronous motor 95 thru a set of bevel gears 98-91 having a 5:1 ratio. 'I'he motor 95 is driven in synchronism with the motor 24 from the power amplier |00, which is controlled by the frequency multiplier |0|, which in turn is controlled by the sawtooth generators 10.

The shaft 88 drives the cam 85 at the same speed as the disc 89 by means of the 1:1 ratio bevel gears 86--81. The cam 85 drives the sprocket intermittently so that the lm 16 is drawn down twice during each revolution of the disc 89. This draw down motion takes place when the slots 90 and 9| are not in line with the axis of the lens system 92-93. =The differential 99 is used to obtain the proper relationship between the slots 90 and 9| and the scanned images. When the slots 90 and 9| are in line with the optical axis of the system one image of refinancel each frame will be completely scanned on the screen of the tube 63' and a photographic record of each frame will therefore be made on the tllm 19 which will include the frame 50 containing the message.

When the iilm 16 is developed and printed it is slowly run thru a standard type of projector until the frame 50 containing the desired message is projected on the screen where it may be read or an enlarged photographic record of it made.

The system may be operated for only a very brief interval of time by opening the circuit oi.'

the video amplifier in the transmitter so that only the synchronizing signal is transmitted. The system could then be put in operation at a predetermined time, the mechanical apparatus synchronized and as the message frame 50 approaches the picture gate I9 the circuit of the video amplifier could be automatically or manually closed and a few frames of the. picture transmited which would include the message frame 50. In this way the signals would be transmitted for only a fraction of a second, thus increasing greatly the secrecy of the system as there would not be time for unauthorized persons to tune in on the video signal.

Although only a few of the various forms in which this invention may be embodied have been shown herein, it is to be understood that the invention is not limited to any specific construction but might be embodied in various forms without departing from the spirit of the invention or uthe scope of the appended claims.

What is called is:

1. The method of secret communication which comprises inserting a. message on a single frame of a standard motion picture film, scanning said nlm, transmitting the images thereof by television. receiving said images at a suitable receiving point, impressing the same photographically on a sensitized motion picture lm at said point.

the transmitted message at a remote point, n

transferring the same onto a sensitized motion picture lm. and developing said'lm to thereby reproduce said message.

3. 'I'he method of secret communication which comprises. inserting a message between picture frames on a standard motion picture lm, scanning said lm, transmitting the images thereof by television, receiving said images at a suitable receiving point, impressing the same photographically on a, sensitized motion picture ilm at said point, and developing said film to reproduce said message together with the transmitted picture in the frame sequence corresponding to that of the lm at the transmitter. A

4. The method of secret communication which comprises the steps o1' inserting a single lm frame area of a graphical message representa.- tion at predetermined spaced positions in a sequence of iilm frame areas of pictorial representations, scanning all of the film frame areas of the graphical and pictorial representations in sequence to produce signalling energy representative of the scanned iilm frames, and transmitting the produced signalling energy with the v two groups oi' signals in an associated and intermingled relationship whereby the signalling energy representative of the graphical iilm frame areas is substantially masked and rendered secret in the transmission by the predominating sequence of picture signalling energy..v

JOHN HAYS HAMMOND, Jn. 

